code: def get_index(self, smiles):
      return self.vmap[smiles]
  
file_path: dgl/examples/pytorch/jtnn/jtnn/mol_tree.py
imports: import copy
  import rdkit.Chem
label_desc: Use image node_id 2 for calling the Vocab obj's underlying member method code with example usage: obj.get_index(smiles) and returns: self